TL;DR — Key Facts
- Build cost per sqm: £2,500 – £3,800 (inner London borough)
- Council planning fee: £548 (householder application, 2026)
- Typical projects: rear extension, side-return, two-storey, wraparound
- Conservation areas: 29 designated areas in Haringey
- Permitted Development: Restricted by Article 4 in some areas
Extension costs in Haringey
Ready to move from budgeting to drawings?
House extension build costs in Haringey typically range from £2,500 to £3,800 per square metre, reflecting Haringey's position as an inner London borough. These figures cover the construction cost only and do not include professional fees, planning fees, or VAT.
On the Harringay Ladder the houses are narrow, so the structural opening at the back is proportionally large and the steel does more work than the plan suggests. In Crouch End and Muswell Hill, sitting inside conservation coverage, the driver shifts to matched brick and joinery on the rear elevation. Same borough, two quite different reasons for a quote to land at the top of its range.
Typical extension costs in Haringey (build only)
On top of the build cost, you will need architectural drawings. These fees are 30% below typical London architect rates.
What affects extension costs in Haringey
The Harringay Ladder is the defining site condition in this borough: long runs of identical Victorian two-up-two-downs with no vehicular rear access at all. Everything is built through the house. Haringey also served 193 contravention notices in three years (MHCLG planning statistics, retrieved 1 September 2026), so work that starts before the paperwork is settled tends to attract a letter.
Conservation areas
Haringey has 29 designated conservation areas, including Highgate Village, Muswell Hill, Crouch End, Tottenham Green, Bruce Castle. If your property is in a conservation area, Permitted Development rights are restricted, meaning you may need a full planning application (£548 council fee). Conservation area applications also tend to require higher-quality materials and more sympathetic design, which can increase build costs by 10-20%.
Article 4 Directions
Haringey has Article 4 Directions in place. Borough-wide Article 4 for HMO conversions. Where Article 4 applies, works that would normally be Permitted Development require a full planning application. This adds £548 to the council fee and typically 2-3 months to the project timeline, which can affect overall costs if you are renting alternative accommodation during the build.
Property type
The housing stock in Haringey is predominantly edwardian terraces in crouch end, muswell hill; victorian two-up-two-downs in harringay ladder; 1930s semi-detached in muswell hill; post-war in tottenham. Victorian and Edwardian terraces typically suit side-return and rear extensions, while 1930s semi-detached properties are well suited to two-storey rear extensions. Detached houses offer the most flexibility but often have larger footprints, meaning higher absolute costs even if the per-sqm rate is similar.
Access and logistics
On a Ladder street the rear garden is reached through the hallway and nothing else. That fixes how the groundworks are done and priced, and it is why extension quotes on these streets cluster tightly - the constraint is identical house to house. Crouch End and Muswell Hill have more variety, with some semi-detached and detached property where a machine can reach the back.
Our drawing fees for Haringey extensions
At Architectural Drawings London. No hourly billing, no surprises. Our fees cover everything needed for a valid planning submission to Haringey Council and for building regulations approval.
Drawing fees for extensions in Haringey
Every package includes a measured survey of your existing property, existing floor plans and elevations, proposed floor plans and elevations, a site plan, and a design and access statement where required. Our MCIAT chartered architectural technologists handle the full process from survey to submission, and we liaise with Haringey Council on your behalf.
We cover all Haringey postcodes: N4, N6, N8, N10, N15, N17, N22.
Planning vs Permitted Development in Haringey
Many house extensions in Haringey can be built under Permitted Development (PD) rights without needing a planning application. Under PD, single-storey rear extensions can extend up to 6 metres from the original rear wall for terraced and semi-detached houses, or 8 metres for detached houses (under the Prior Approval process). However, Haringey has Article 4 Directions that may remove some PD rights. Borough-wide Article 4 for HMO conversions.
Haringey's 29 conservation areas are concentrated in Crouch End and Muswell Hill rather than spread evenly, so the first question is whether your street is designated at all. On the Harringay Ladder terraces the side-extension rule is moot; matched brick and joinery are what count. On the Muswell Hill semis the side restriction is the real loss.
Two-storey extensions require full permission. On the Harringay Ladder the houses are narrow and the rear projections are paired, so a first floor above the back addition sits directly alongside the neighbour's and light to their rear rooms becomes the central question. Crouch End and Muswell Hill have deeper plots but heavier conservation coverage, which moves the argument to the elevations instead.
Haringey issued 1,023 certificates of lawful development in three years (MHCLG planning statistics, retrieved 1 September 2026). In the borough that serves the second-highest number of contravention notices in London, the certificate is the document that answers one before it is sent. It is prepared from the same measured survey as the build drawings, so taking it adds little beyond the council's fee.
Frequently asked questions
How much does a house extension cost in Haringey?
Build costs for a house extension in Haringey typically range from £2,500 to £3,800 per square metre, as Haringey is an inner London borough. A typical single-storey rear extension of 15-20 sqm would cost between £37,500 and £76,000 for the build alone. On top of build costs.
Can I extend under Permitted Development in Haringey?
Across Haringey's 29 conservation areas, the coverage is concentrated in Crouch End and Muswell Hill rather than spread evenly, so the first question is whether your street is in one at all. Where it is, matched brick and joinery on the rear elevation carry most of the weight, and the Article 4 Direction removes further rights independently of the designation.
How long does a house extension take in Haringey?
A typical house extension project in Haringey takes 5-8 months from initial instruction to completion. This breaks down as: 2-3 weeks for measured survey and drawing preparation, 8 weeks for planning determination by Haringey Council (if required), 2-4 weeks for building regulations approval, and 8-16 weeks for construction depending on the size and complexity of the extension.
Do I need a Party Wall Agreement for an extension in Haringey?
Two adjoining owners on a Ladder terrace, each entitled to their own notice and their own surveyor. Rear extension foundations will sit within three metres of both. Because so many houses on these streets have already been extended, the adjoining structures are often themselves recent, which makes the schedule of condition more useful rather than less.
What experience do you have with extensions in Haringey?
We prepare extension drawings for properties across all Haringey postcodes (N4, N6, N8, N10, N15, N17, N22). Our MCIAT chartered architectural technologists understand Haringey Council's policies, design guides, and local precedents. We have a council-ready drawing review across all 33 London boroughs.
